6 Ways to Tell Seedlings from Weedlings

22 March 2018, written by Ann Marie Hendry

With the spring equinox behind us it’s time to start thinking about sowing outdoors, direct into the soil. But this is fraught with uncertainty. Whether you’re new to growing or are growing something new, how do you know which of those eager little seedlings have sprouted from seeds you sowed, and which are sneaky little weeds taking advantage of your fertile garden soil?

I will hold my hand up and admit that I have, in the past, accidentally weeded out the plants that I have carefully sown. (Okay, maybe it was more than once!) Rather than beat myself up about it, I prefer to believe that the essence of good gardening is to learn from my mistakes. So here are six sure-fire ways to tell your seedlings from your weedlings...

1. Use Markers to Identify Rows of Seedlings

When sowing in rows, mark the beginning and end of the row so you know exactly where to expect seedlings to appear. You can use whatever you like for this – plant labels, sticks, pebbles, bits of broken terracotta pot – anything, in fact, that won’t blow or wash away.

Use markers at the end of rows so you know exactly where to expect your seedlings to grow

For extra certainty and ruler-straight rows, spool out string between two sticks or pegs and sow along the line of it. Anything growing more than an inch or so out of line is bound to be a weed.

You can also backfill drills with compost instead of garden soil. The strip of compost will be darker than the surrounding soil so you’ll know precisely where you’ve sown, plus it will provide a small boost of additional nutrients for your emerging seedlings.

2. Plant a Control Group

When sowing outdoors, fill a small pot with a sterile seed starting mix and sow a few seeds into that too. Place it at the end of the row. When seedlings start to pop up, just refer to the pot to check if what’s growing in the soil matches what has sprouted in the pot.

Sow a few seedlings in a pot so you can compare with the seedlings that pop up in the garden

This is particularly useful when broadcasting seed or sowing a seed mixture that has a variety of leaf shapes, for instance a mesclun salad mix.

3. Know Your Germination Times

The seed packet will normally tell you how many days or weeks after sowing you can expect germination to occur. Anything that pops up sooner or later than the anticipated germination window should be placed under suspicion!

Know your germination times to help identify which seedlings are weeds

4. Wait Until the True Leaves Appear

Most seedlings have two seedling leaves (some, such as onions, have just one). These may bear no resemblance to the leaves of the adult plant, which complicates identification of very young seedlings.

Patience is a virtue, so my mother keeps telling me, and in this case it’s true. Before long, all plants will supplement their seedling leaves with their first true leaves. These are miniature versions of the adult leaves. If you already know what the adult leaves look like, you’ll now be able to tell which ones are your seedlings. Wait until they have four or five true leaves if you’re still unsure.

If you don’t know what to expect, compare with a picture of the plant you’re growing – perhaps from the seed packet – and invest in a well-illustrated wildflower book showing what commonly grows wild in your region.

The seedling leaves on this pepper plant are smooth, while the true leaves show veins and are a different shape

5. Watch and Learn

Experience is the best education. Pay attention to your garden and you’ll soon learn what the seedlings of your favourite vegetables look like, as well as those weeds that inevitably spring up year after year. Take photographs of what you’re growing so you can look back at them the next time you’re sowing. Take photos of the weeds too!

6. Pre-sprout Weeds

You can also reduce the number of weeds you’ll need to deal with overall by pre-sprouting them. It sounds counter-intuitive to encourage weeds to germinate, but I promise this will actually make weeding easier! It’s a good technique to help you learn to identify the weedlings that commonly sprout in your garden, plus it cleans the soil so you have fewer weeds to deal with after your seeds have germinated.

Tunnel cloches can help to pre-sprout weeds for easy removal before sowing time

To pre-sprout your weeds, cover your planting area with clear plastic, a tunnel cloche, or a cold frame. Do this a few weeks before you’re ready to plant. The added warmth will speed up germination of the weeds. Just before you’re ready to plant, hoe off any annual weeds or pull out tenacious perennials such as buttercups and willowherb.

You can then sow your seeds into weed-free, warm soil that will give them a superb start in life.

Comments

"Thank you Ann Marie, planting a control group is definitely a remarkable tip. This year I tried to learn more about biofumigation as I had a very bad experience last year with wire worms. Well the Raphanus sativus was easy to tell as it looks like most of the brassicaceas. But I'm still pretty unsure about Malva verticillata within the seedmix I used. But I'll get there :)"Elaon Friday 13 April 2018

"It will be a great learning experience Ela! "Ann Marie Hendryon Wednesday 18 April 2018

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